Changes in toxicity and bioavailability of lead in contaminated soils to the earthworm Eisenia fetida (Savigny 1826) after bone meal amendments to the soil

The effect of bone meal (Ca-5(PO4)(3)OH) amendments on lead (Ph) bioavailability to Eisenia fetida (Savigny 1826) was investigated. A standard uncontaminated soil was amended with Pb(NO3)(2) solution to give Ph concentrations of 7,000 mug/g of soil. After one week, bone meal was added to one half of the soil in the ratio 1:20 bone meal:soil. Immediately after addition of the bone meal, survival times of E. fetida were 23 and 41 h in the bone meal-free and bone meal-amended soil, respectively. Twentyeight days after addition of the bone meal, survival times of Eisenia fetida were 67 h in the bone meal-free soil and more than 1 68 h in the bone meal-amended soil. In a second experiment, a standard Organisation for Economic Co-operation and Development reproduction toxicity test was carried out, but in addition to Pb(NO3)(2) solution, bone meal was added to the soil in the ratio 1:20 bone meal:soil. The bone meal-free soil was left for five weeks before addition of E. fetida. In the bone meal-amended soil, bone meal was added to the soil one week after addition of the Ph. The soil was left for a further four weeks before addition of Eisenia fetida. Calculated toxicities were significantly lower for the bone meal-amended soil than those calculated for the bone meal-free soil. Twenty-eight-day median lethal concentrations (LC50s; concentration that is statistically likely to kill 50% of the exposed test organism within a given time period +/- 95% confidence intervals) of Ph were 4,379 +/- 356 mug/g of soil for bone meal-free soil and 5,203 +/- 401 mug/g of soil for bone meal-amended soil. Twenty-eight-day median effect concentrations (EC50s; concentration causing a reduction by 50% of a stated parameter) of Pb for weight change were 1,408 +/- 198 mug/g of soil for bone meal-free soil and 3,334 +/- 731 mug/g of soil for bone meal-amended soil and EC50s for cocoon production were 971 +/- 633 mug/g of soil for bone meal-free soil and 1,814 +/- 613 mug/g of soil for bone meal-amended soil. Significant mortalities occurred at Ph concentrations of 2,000 mug/g of soil in the bone meal-free soil and 5,000 mug/g of soil in the bone meal-amended soil. Earthworm Ph body load was lower in the bone meal-treated soil than in the bone meal-free soil up to a Ph concentration of 5,000 mug/g of soil. Earthworm Pb body load was approximately 100 mug/g of worm in surviving earthworms in both experiments when significant mortality occurred. Water and diethylenetriamine pentaacetic acid-extractable soil Ph showed good correlations with earthworm Ph body load. These extractions could be used as estimates for Pb bioavailability.